Condenser (Central A/C); Condenser Fan Control - PREVOST H3-41 Maintenance Manual

SECTION 22: HEATING AND AIR CONDITIONING
4.4

CONDENSER (CENTRAL A/C)

The central A/C system condenser coil is hinge mounted on the R.H. side of the vehicle on the condenser
compartment door. Since condenser's purpose is to dissipate heat from the hot refrigerant, it is important
to keep the cooling coils and fins clean. A clogged coil will cause high discharge pressure and insufficient
cooling.
FIGURE 43: CENTRAL A/C CONDENSER
4.4.1

Condenser Fan Control

Four brushless motors fan are installed in condenser compartment on R.H. side of vehicle in order to
ventilate the condenser coil. The fans pull outside air through the condenser coil and discharge it through
an opening at bottom of compartment.
Fan speed is controlled by the multiplex program and varies according to high side pressure. A Pulse
Width Modulation (PWM) signal is used to control fan speed.
You will notice fan speed ramp up to full speed between 100 psi and 200 psi, and a ramp down from 200
psi to 100 psi. Below 100psi, the fans are not running. Refer to Figure 44 below.
NOTE
During normal conditions, fan function according to the following specifications:
Full speed: 6200cfm, 37A at 28 VDC
Fan motor speed: 2950 rpm at full speed
32 PA1621 Maintenance Manual All Series | Revised February 2019